N-2 reduction by nitrogenase involves the accumulation of four reducing equivalents at the active site FeMo-cofactor to form a state with two [Fe-H-Fe] bridging hydrides (denoted E-4(4H), the Janus intermediate), and we recently demonstrated that the enzyme is activated to cleave the N N triple bond by the reductive elimination (re) of H-2 from this state. We are exploring a photochemical approach to obtaining atomic level details of the re activation process. We have shown that, when E-4(4H) at cryogenic temperatures is subjected to 450 nm irradiation in an EPR cavity, it cleanly undergoes photoinduced re of H-2 to give a reactive doubly reduced intermediate, denoted E-4(2H)*, which corresponds to the intermediate that would form if thermal dissociative re loss of 142 preceded N-2 binding. Experiments reported here establish that photoinduced re primarily occurs in two steps. Photolysis of E4(4H) generates an intermediate state that undergoes subsequent photoinduced conversion to [E-4(2H)* + H-2]. The experiments, supported by DFT calculations, indicate that the trapped intermediate is an Hy complex on the ground adiabatic potential energy suface that connects E-4(4H) with [E-4(2H)* + H-2]. We suggest that this complex, denoted E-4(H-2; 2H), is a thermally populated intermediate in the catalytically central re of Hy by E-4(4H) and that N-2 reacts with this complex to complete the activated conversion of [E-4(4H) + N-2] into [E-4(2N(2)H) + H-2].